chacha20: adding 64-bit counter support #359
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…ST_BLOCKS sizes, but 4 and 10 were failing, among others. Problem was the 64-bit addition was not being applied properly when adding the counter to the state prior to writing blocks to the dest
tarcieri
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Jul 30, 2024
tarcieri
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Addresses #334
The constant booleans in the backends should be evaluated at compile-time... but there's a slight chance that I could write a test for the
ChaCha20Rngthat fails onaarch64with neon. The originaladd64macro does what the name suggests, it adds vectors in a 64-bit fashion, meaning that it could perform addition incorrectly when the counter should be 32 bits and the counter is exceeding theu32::MAX.This shouldn't be an issue with the
ChaCha20cipher sincecipherpanics when the counter will exceedu32::MAX, butChaCha20Rngwraps around and is currently supposed to use a 32-bit counter. I'm going to write one more test to see if I can get it to fail, and if it fails, then I'll probably need to changeadd64to accept a boolean for performing 32-bit or 64-bit addition.